Wednesday, February 18, 2009

Pilot Action May Have Led to Crash

Investigators examining last week's Continental Connection plane crash have gathered evidence that pilot commands -- not a buildup of ice on the wings and tail -- likely initiated the fatal dive of the twin-engine Bombardier Q400 into a neighborhood six miles short of the Buffalo, N.Y., airport, according to people familiar with the situation.

The commuter plane slowed to an unsafe speed as it approached the airport, causing an automatic stall warning, these people said. The pilot pulled back sharply on the plane's controls and added power instead of following the proper procedure of pushing forward to lower the plane's nose to regain speed, they said. He held the controls there, locking the airplane into a deadly stall, they added.

The crash on Feb. 12 at about 10:20 p.m. EST killed all 49 aboard and one person on the ground.

View Full ImageA New York State trooper guides an overhead crane Tuesday to the crash site of Continental Connection Flight 3407 near Buffalo, N.Y.Reuters

A New York State trooper guides an overhead crane Tuesday to the crash site of Continental Connection Flight 3407 near Buffalo, N.Y.A New York State trooper guides an overhead crane Tuesday to the crash site of Continental Connection Flight 3407 near Buffalo, N.Y.A New York State trooper guides an overhead crane Tuesday to the crash site of Continental Connection Flight 3407 near Buffalo, N.Y.

The investigation is still at an early stage, and National Transportation Safety Board officials have warned about ruling out potential causes or prematurely jumping to conclusions. But in the past few days, government and industry crash experts have gained a better understanding of the sequence of events as they have compared information from the plane's flight recorders with radar and weather data.

Mark Rosenker, the NTSB's acting chairman, said Tuesday that investigators still have "lots of data that needs to be examined," and "still more evidence that needs to be collected," before announcing firm conclusions.

The Q400 was operated by Colgan Air Inc., an unit of Pinnacle Airlines Inc., which was operating the flight on behalf of Continental Airlines Inc. Joe Williams, a spokesman for Pinnacle, declined to comment about details of the accident while the safety board was investigating. A spokeswoman for the Air Line Pilots Association, which represents the pilots, declined to comment.

Investigators initially focused their attention on potential ice buildup on the plane's wings -- a perpetual hazard of aviation. People familiar with the investigation cautioned that they still aren't sure whether icing may have played a contributing role in the crash because it was on the minds of the pilots, but they noted that another Q400 flew through "moderate" icing conditions on the same route from Newark, N.J., to Buffalo the same night, landing without incident less than an hour after the crash.

A Bombardier spokesman said Tuesday that the company is "not aware of any serious icing incident on this aircraft" since it was introduced into service in February 2000.

According to people familiar with the investigation, Capt. Marvin Renslow, 47 years old, who lived outside Tampa, Fla., was at the controls of Flight 3407. The safety board said Mr. Renslow was relatively new to the Q400, which he began flying only in December, when he upgraded from another type of airplane. First Officer Rebecca Lynne Shaw, 24, of Seattle, had accumulated 774 hours in the 74-seat aircraft.

The recovered flight data described in detail how the crew of Continental Flight 3407 handled the emergency, the people said.

During the flight from Newark, Mr. Renslow and Ms. Shaw noticed ice building up on the windshield and wings of the airplane after they had already activated the craft's de-icing system, which inflates a series of rubber bladders on the leading edge of the wings and tail surfaces to break up accumulated ice.

According to the plane's flight recorders, Flight 3407's descent into Buffalo was routine until roughly a minute before impact, when the crew lowered the landing gear, followed by the command to extend the wing flaps, which enable the plane to fly at slower speeds.

Almost immediately, these people say, the plane's air speed slowed rapidly, causing a stall-warning device known as a "stick-shaker" to cause the pilots' control column to vibrate. This was followed by a "stick-pusher," which automatically forces the stick forward.

At this point, the captain appears to have pulled back with enough force to overpower the stick-pusher and shoved the throttles to full power, according to people familiar with the matter. Safety board officials said the nose pitched up to a 31-degree angle. Already at a dangerously low speed, the wings immediately stopped generating lift. The plane whipped to the left and then entered a steep right turn, losing 800 feet of altitude in less than five seconds. At one point the right wing was perpendicular to the ground, according to information taken from the flight data recorder.

The pilots continued to fight with the controls almost all the way to the ground, and in the final moments, "it appeared that they were beginning to make headway when they ran out of altitude," said one person who looked at the data.

A crash with many similarities occurred five years ago involving a regional jet operated by Pinnacle. Following that crash, which killed the two pilots outside Jefferson City, Mo., the safety board urged Pinnacle and other commuter operations to revamp training procedures, including how to recover from certain types of stalls. Investigators are seeking more information from Pinnacle about how it changed its procedures in the wake of the previous crash, as well as specific details about the training provided for the pilots on Flight 3407.

Pinnacle's Mr. Williams said that following the previous crash, "we continually evaluated our procedures in accordance with our commitment to safety."